Slicing machines are used for slicing blocks of meat, meat products and other food products such as cheese. Typically they include a rotating blade having a spiral cutting edge, or a rotating blade having a circular cutting edge which is mounted for orbital motion so that upon each rotation of the spiral cutting edge blade or each orbit of the circular cutting edge blade its cutting edge moves across the face of a block of product to cut a slice from it. The block of product is fed stepwise and moves when the cutting edge is out of contact with it or is fed forwards continuously so that the cutting edge follows a generally helical path through the block. Conventionally the block of product rests on a stationary bed and is driven forwards towards the blade by a pusher having a gripper or suction pad which engages the rear face of the block of product. In this case a spring loaded paddle usually bears downwards on the block of product to steady it towards its downstream end.
It is also known to replace the stationary bed and pusher by a pair of opposed driven conveyors having their adjacent faces arranged to be driven in the same direction. An example of a slicing machine with such a feeding device is shown in U.S. Pat. No. 3,162,226 which has the pair of opposed conveyors mounted above and below the block of product. The spacing between the opposed conveyors is manually adjustable and the upper conveyor is mounted at about its mid-point by a spring loaded connection which can accommodate small variations in the height of blocks of product. Such arrangements are particualrly useful because they enable blocks of product to be fed successively so that they can be sliced with substantially no interruption between them and they avoid the need for interrupting the slicing whilst the pusher is withdrawn and a further block is located on the stationary bed.
One problem however with this type of arrangement is that although the downstream end of the conveyors approach the plane of cut of the blade because of the curvature of the end rollers of the conveyor the last 30 to 40 mms of each block is substantially unsupported. As this portion is cut by the blade the blade tends to grab the block and pull it too far downstream so cutting slices that are thicker than required. This problem is exaggerated still further in the arrangement shown in U.S. Pat. No. 3,162,226 because of the way in which the upper conveyor is connected at about its mid-point by a spring loaded connection. This results in the end portions of each block being inadequately held. In an attempt to overcome this U.S. Pat. No. 3,162,226 includes an additional plate which engages the cut face of the block of product and supports the cut face in position as the blade moves towards it. This additional plate oscillates back and forth with the cutting edge of the blade.
It is known that the quality of slices cut by a slicing machine is very dependent upon the support and control of the movement of the block of product and particularly the support and control of the movement of the end portion of the block of product. Many other attempts have been made to support the product as firmly as possible and as close as possible to the plane of cut of the blade. Meat and similar food products are flexible and somewhat fragile. If they are not held firmly enough the block tends to be pulled as the blade is cutting a slice from its face as has already been mentioned. This problem is particularly bad for blocks having non-parallel sides. Meat such as sides of bacon are a natural product and even after they have been subjected to a pressing operation their sides are not flat and certainly not parallel. Molded products such as molded meat products and cheese often have sides which are flat but are not parallel to one another since the mold includes a taper to enable the product to be de-molded. Thus even if opposite side faces of such molded products are flat they are often not parallel.
A significant attempt to overcome all of these problems is disclosed in GB-A-2133279 which discloses a slicing machine including a rotatable blade and a feeding device for feeding blocks of product towards the blade, the feeding device being divided in a direction transverse to its feed direction into a number of separate elements pivotally connected to a common support and having a ganged drive and biasing means which, in use, urge the separate elements adjacent the blade independently towards the block of product so that the separate elements pivot independently and hold a block of product the thickness of which is not uniform in the transverse direction. In this example the separate elements are formed by rollers which engage only the downstream end of the block of product which include backwardly facing teeth to resist the forwards pull of the knife-blade. The rollers are supported by a pivoted parallelogram-type linkage but, nevertheless, as the rollers pivot and move towards the block of product they tend to move further away from the plane of cut of the blade and so support the product less effectively.
This British specification is a further improvement over an earlier attempt to hold securely the last portion of a block of product which is described in U.S. Pat. No. 4,329,900. In this earlier specification only a single roller is pivotally mounted and arranged to bear against the downstream end of a block of product. Since the arrangement shown in this earlier specification only uses a simple pivot rather than a parallelogram linkage the roller tends to move even further away from the plane of cut of the blade as it pivots towards the block of product.
The feeding device disclosed in these two specifications undoubtedly supports the end portions of each block of product more firmly and as close as possible to the plane of cut of the blade than the conventional arrangement such as that disclosed in U.S. Pat. No. 3,162,226. However, they both tend only to engage the product to both feed it and prevent the forward pull from the blade along a single line of contact which, particularly with delicate products leads to damage of the product.